Multi-Axial Expandable Pedicle Screw and an Expansion Method Thereof

ABSTRACT

The invention disclosed a multi-axial expandable pedicle screw and an expansion method by using the same. Structure of the screw comprising a hollow screw being spherical shaped end connecting with an adapting piece, which is universal joint structure; an inner wall of the adapting piece connecting a lock bolt through screw threads; the hollow screw with sharp shaped on another end having a bore inside formed hollow structure in its entirety; the bore having taper shaped tip; expansion gaps uniformly setting up two, or three or four or more anterior fins on the hollow screw along its axial direction upward, prolonging from its tip to the bore; the inner needle is disposed in the bore. The invention can reduce the pedicle screw loose and even occurrence ratio of pull-out and increase the stability and reliability and reduce the failure rate of spinal surgeries at the same time. It is also easy to operate, and degree of expansion is of controllable level.

FIELD OF THE INVENTION

The invention relates to medical apparatus, particularly, to a pedicle screw used in spinal surgeries, and more particularly, to a multi-axial expandable pedicle screw and an expansion method by using the same.

BACKGROUND OF THE INVENTION

In order to fulfill treatment of spinal diseases such as degenerative disorders, spinal trauma, spinal tumor, and spinal deformity and like, a method of the transpediclular internal fixation with satisfactory results has been widely used all over the world at present. The multi-axial pedicle screw traditionally is as an entire screw-thread solid structure in common international circumstance. The fixation strength of the said screw depends on the contact area of the screw-thread and the bone, as well as the strength of vertebrae per se. However, it usually is not possible to make a slipped vertebrae reduction, maintain a strong fixation strength while fixation and a sustainable holding force after fixation. As a result, a failure of vertebrae reduction and fixation or unsatisfied anatomical reduction may occur, thus, miss the meaning of the surgery. Especially, a failure due to an operated screw loosing, or even pulling out, often occurs, when patients suffer osteoporosis or perform improper activities after surgery.

Previously, the Chinese patent in utility model numbering 03262479.4 disclosed an expansion method by using an expandable screw, comprising a barrel-shaped outer cannular screw, and a gauge screw. A screw thread and square for the use of hold are set at the end. Four uniformity expansion parts cut on the tip of outer cannular screw along its axis. A contact mechanics mode of both the pedicle screw and the vertebrae has changed by means of mechanical expansion provided by the patent in utility model. Thus the contact mechanics mode of the screw and screw path has changed when tweaking into the gauge screw for effectively improving fixation strength. Moreover, Chinese patent in utility model numbering 03235808.3 disclosed another kind of hollow pedicle screw processing connecting screw thread on both its inner and outer walls, and expansion screw rotationally installed in a cavity of the pedicle of vertebral arch screw. The lower part of the cavity of the pedicle of vertebral arch screw is inner cavity structure processing at least three expanding gaps vertical downwards extension on its wall and have an end for holding. The purpose of the patent in utility model is of increasing fixation strength (anti-pulling out) of the pedicle screw. Disadvantages of both patents are uneasy to insert the gauge screw in a way of tweaking during an operation. As mentioned above, it could be seen that operating steps for a surgeon increase and fixing the end part with others is in mono-direction which contradicts inner spinal fixing operation in multi-directions and multi-angles requirements. Further, a depth of tweaking the gauge screw operated by surgeons are different in fulfilling expandable method and differences of expandable degree between screws occurs, so as to influence treatment effective and uniformity of the product.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned lack of available technology, the invention aims to provide the multi-axial expandable pedicle screw and an expansion method by using the same to reduce the rate of screw loosening. It can increase the stability and reliability at the same time. Being in multi-axial, multi-angle connection with other components, it is also easy to operate, and degree of expansion is of controllable level. More particularly, the invention can be not only to simplify surgery procedure steps, but also to ensure to get the same level of expansion with the same specification of the screw by adopting rod-press design.

In order to achieve above objective, the invention of the technical solution is as follows: the multi-axial expandable pedicle screw, includes a hollow screw, with a tip on an end, having a bore or blind hole inside formed hollow structure in its entirety; the bore, taper shaped on its top, allowing an inner needle disposed in; expansion gaps uniformly setting up on the screw from its tip along its axial direction upward to the bore; the inner needle, inserted in the bore, having a length more than the bore's footage; another end of the screw of spherical shaped end connecting with an adapting piece, which is universal joint structure having a cavity with an open pore; an inner wall of the adapting piece at the open pore connecting a lock bolt for sealing through the screw thread on the inner wall and a end coupler; a fixation rod mounting in the cavity above the inner needle to press the inner needle.

Wherein, the spherical shaped end is actively positioned under the adapting piece at its open pore through an annular pad and an erection cap; the annular pad can be either an opening structure or an enclosed structure; an aperture is designed in the centre of the erection cap; the inner needle and the bore to fit with are taper shaped at their tips respectively, in which an angle of the taper of the inner needle is equivalent to an angle of the taper of the bore at its tip or less; and the inside diameter of the inner needle matches the outer diameter of the bore; the length of the inner needle is more than a path of the bore, and its exposed part outside of an opening of the bore is 0.5˜3.0 mm, preferably 0:8˜1.5 mm; the expansion gaps are of 60%-70% of the total length of the screw, structured by splitting grooves to form two or more anterior fins, staring from the tip of the screw along its axial direction upward to the bore; anterior fins are curve shaped; the adapting piece in connection with the screw forms U shape in its entirety; on the spherical shaped end of the screw there is a regular polyhedron shaped concave.

Further more, an additional annular pad being either an opening structure or an enclosed structure is needed to be placed in between the inner needle and the fixation rod.

The expansion method of multi-axial expandable pedicle screw, adopting multi-axial, multi-angle connecting method with other medical parts; fulfilling press operation to the inner needle positioning in the bore of the screw through rod-press technique to controllably complete expansion process to the screw, enabling the screw to expand to 2˜3 mm based on an original diameter.

The invention has significant features as following:

1. The present invention employing the rod-press technique to change contact mode of the screw and vertebrae through mechanical expansion principle, can effectively improve the fixation strength of the pedicle screw, meanwhile can obtain a user-friendly features, simple process character, and also ensure that of homogeneity of degree of screw expansion. 2. The present invention adopting the adapting piece with universal jointer, is able to provide adjustment function for fixing the screw with multi-axial and multi-angle and function of angle of fixation, which makes the screw in connection with other spinal internal fixation devices more convenient and effective, so that it can be used for a variety of the spinal orthopedic and internal fixation surgeries due to doctor-friendly operating features. 3. The present invention adopting realized 2˜3 mm expansion purposes on a basis of the original diameter of the screw in a way of controllable expansion by defining the length of the inner needle, the length of the bore, and an angle correlation of two ends of the inner needle and the bore, accordingly the expansion degree (expansion is not the bigger the better) is controlled. The controllable expansion method plays an extremely important role in the spine surgeries. 4. The present invention sets the appropriate length of expansion space or gaps, which only to expand in the vertebrae body, not a full-length of the screw for avoiding a risk of a pedicle burst result from a full-length expansion. Therefore, the present invention provides a new technical line of control led expansion technology.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structure of this invention.

FIG. 2 is a structure of the screws of this invention.

FIG. 3-1 is an implementation of an expansion process of this invention (the inner needle is not inserted).

FIG. 3-2 is the implementation of the expansion process of this invention (the inner needle is inserted).

FIG. 3-3 is the implementation of the expansion process of this invention (the inner needle downward after squeezing).

FIG. 4 is a structure of the invention of another example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be described in detail in connection with specific embodiments with reference to the accompanying drawings.

Example 1

Referring to FIGS. 1 and 2, the expansion method of multi-axial expandable pedicle screw, adopting multi-axial, multi-angle connecting method with other medical parts; fulfilling press operation to the inner needle positioning in the bore of the screw through rod-press technique to controllably complete expansion process to the screw, enabling the screw to expand to 2˜3 mm based on an original diameter.

Wherein, the length of the inner needle positioning in the bore of the screw is bigger than the path of the bore. The part exposed outside of the opening of the bore is 0.8˜1.5 mm (here is 0.8 mm). The expansion gaps are of 60%-70% of the total length of the screw (60% is in this example), structured by splitting grooves, staring from the tip of the screw along its axial direction upward to the bore. Tip of anterior fins are curve shaped for avoiding a risk of pedicle fracture. The inner needle is inserted in the bore so that an inconvenient operation by tweaking can be avoided. The inner needle and the bore to match with are of taper shaped at their tip ends respectively in which the angle of the taper of the inner needle at its tip equals the angle of the taper of the bore at its sharp end or less (it is equal in this example). And the outer diameter of the inner needle matches the inside diameter of the bore for easy fulfilling press in after inserting the inner needle to realize expansion process of the screw and enabling the screw expands to 2˜3 mm in comparison with previous size to complete a controllable expansion.

The multi-axial expandable pedicle screw by using the expansion method the afore-mentioned comprising the hollow screw 1 having spherical shaped end 2 on one end and the tip shaped on another one end, in which the spherical shaped end 2 actively connects with the adapting piece 4; the bore or blind hole 7 having taper shape on its top is in a centre of the screw, expansion gaps 9 structured by splitting with one groove to form two anterior fins, staring from the tip of the screw 1 along its axial direction upward to the bore 7 (not to full length, for example, expansion gaps is 21 mm for the screw of 35 mm length); anterior fins being curve shaped; the spherical shaped end 2 actively positioning under the adapting piece 12 at its open pore through the annular pad 5 and the erection cap 12 (the annular pad 5 can be either an opening structure or an enclosed structure positioning under the spherical shaped end 2 while the erection cap 12 being above the spherical shaped end 2). When screwing the lock bolt 6 for sealing down from top end of the adapting piece 4 through the screw thread, the fix rod 10 is gradually pressed down in order to push the inner needle 8 to top end of the bore 7 completing expansion process, meanwhile, the spherical shaped end 2 stably fixed in the universal joint structured adapting piece 4 without breaking away from it.

The adapting piece 4 being as the universal joint structure forms U shape in its entirety. The adapting piece connects the spherical shaped end 2 of the screw 1 at lower position functioning multi-axial and multi-angle a screw adjustment. The inner wall of the U shape at its upper open pore connects the lock bolt 6 for sealing through the screw thread and the end coupler. For pressing the inner needle 8, the fixation rod 10 is mounted in the cavity of the screw, above the inner needle 8 inserting in the bore.

The inner needle 8 forms taper shape at its tip. The inside diameter of the inner needle matches the outer diameter of the bore 7 (the both are the same size in this example. Both match with each other by a gap or a clearance in between. There is no an inner screw thread in the bore 7 and outer screw thread outside of the inner needle 8 which is inserted in the bore). The length of the inner needle 8 is more than the path of the bore 7, particularly, more than the open pore on the bore, 0.8 mm can be exposed outside of the opening of the bore, for instance, after inserting into the bore.

Referring to FIG. 3-1 and 3-2, to make of use of the present invention, planting the hollow screw 1 holding by a tool to the pedicle by holding the regular polyhedron shaped concave (six regular polyhedron shapes in this example) with a tool, then inserting the inner needle 8 into the bore 7 of the screw 1; placing the fixation rod 10 in the adapting piece 4; directly pressing the inner needle 8 by tweaking the lock bolt 6; gradually pressing the fixation rod 10 during tweaking the lock bolt 6 to make the tip part of explosion of the inner needle 8 against into the tip of the bore 7 resulting in the expansion gaps 9 at the top end of the screw 1 to be opened gradually forming a taper shape; 2 mm expansion gaps is expanded based on the original diameter in this example. This ensure to meet medical requirements and purpose of enhance anti-pulling out force. The expansion gaps can be restored by tweaking out the lock bolt 6 and taking the inner needle 8 out. The screw 1 can be tweaked out if the position of the screw 1 is not properly.

Example 2

Referring FIG. 4, the example refers to Example 1 with the exception of: adding the annular pad 11 (it can be either an opening structure or an enclosed structure) between the inner needle 8 and the fixation rod 10 for preventing contacting surfaces of the inner needle 8 and the fixation rod 10 from damage; To take 45 mm in length of specification of the screw as an example, the fins of the expansion gaps 9 are 4 and length of the screw is lengthened 31 mm which is of 70% of the screw in total. After inserting into the bore, the inner needle 8 can be exposed outside of the upper opening of the bore with 1.5 mm. 3.0 mm is expanded in comparison with the original diameter of the screw in this example.

Referring to making of use of the present invention, planting the hollow screw 1 holding by a tool to the pedicle by holding the regular polyhedron shaped concave (Four regular polyhedron shapes in this example) with a tool, then inserting the inner needle 8 into the bore 7 of the screw 1; placing the fixation rod 10 in the adapting piece 4 above the annular pad 5; directly pressing the inner needle 8 by tweaking the lock bolt 6; gradually pressing the fixation rod 10 during tweaking the lock bolt 6 to make the tip part of explosion of the inner needle 8 against into the tip of the bore 7 through the annular pad 5 resulting in the expansion gaps 9 at the top end of the screw 1 to be opened gradually and fins at top of the screw form a taper shape as well; 2 mm expansion achieved based on the original diameter in this example. This ensure to meet the medical requirements and the purpose of enhancing fixation strength.

Example 3

The example refers to Example 1 with the exception of: the inner needle 8 and the bore to match with are taper shape at their tip ends respectively in which angle of the taper of the inner needle is less than the angle of the taper of the bore; and the inside diameter of the inner needle matches the outer diameter of the bore for inserting connection; To take 40 mm in length of specification of the hollow screw as the example, the fins of the expansion gaps 9 are 3 and length of the screw can be lengthened 26 mm which is of 65% of the screw in total. After inserting into the bore, the inner needle exposed outside of the upper opening of the bore is 3.0 mm. 2.5 mm expansion was achieved in comparison with the original maximum diameter of the screw in this example ensuring to meet surgical requirement.

Example 4

The example refers to Example 1 with the exception of: the inner needle 8 and the bore to match with are taper shape at their tip ends respectively in which the angle of the taper of the inner needle is less than the angle of the taper of the bore; To take 40 mm in length of specification of the hollow screw as the example, the fins of the expansion gaps 9 are 4 and length of the screw can be lengthened 28 mm which is of 70% of the screw in total. After inserting into the bore, the inner needle 8 exposed outside of the upper opening of the bore is 0.5 mm. 2.2 mm was expanded in comparison with the original maximum diameter of the screw in this example ensuring to meet surgical requirement.

Example 5

The example refers to Example 1 with the exception of: the inner needle 8 and the bore to match with are taper shape at their tip ends respectively in which the angle of the taper of the inner needle is less than the angle of the taper of the bore; To take 40 mm in length of specification of the hollow screw as the example, the fins of the expansion gaps 9 is 2 and length of the screw can be lengthened 24 mm which is of 60% of the screw in total. After inserting into the bore, the inner needle 8 exposed outside of the upper opening of the bore is 1.1 mm. 2.2 mm was expanded on basis of the original maximum diameter of the screw in this example ensuring to meet surgical requirement. 

1. A multi-axial expandable pedicle screw, includes a hollow screw, with a tip on an end, having a bore inside formed hollow structure in its entirety; the bore, taper shaped on its top, allowing an inner needle disposed in; expansion gaps uniformly setting up on the screw from its tip along its axial direction upward to the bore; characterized in that the inner needle inserted into the bore having a length more than the bore's footage; another end of the screw being spherical shaped end connecting with an adapting piece, which is universal joint structure having a cavity with an open pore; an inner wall of the adapting piece at the open pore connecting a lock bolt for sealing through the screw thread on the inner wall and a end coupler; a fixation rod mounting in the cavity above the inner needle to press the inner needle.
 2. The multi-axial expandable pedicle screw of claim 1, characterized in that wherein the spherical shaped end actively positions under the adapting piece at its open pore through an annular pad and an erection cap.
 3. The multi-axial expandable pedicle screw of claim 2, characterized in that wherein the annular pad being either an opening structure or an enclosed structure; an aperture is designed in the centre of the erection cap.
 4. The multi-axial expandable pedicle screw of claim 1, characterized in that wherein the inner needle and the bore to fit with are taper shaped at their tips respectively, in which an angle of the taper of the inner needle at tip is equivalent to an angle of the taper of the bore at tip or less; and the inside diameter of the inner needle matches the outer diameter of the bore.
 5. The multi-axial expandable pedicle screw of claim 1, characterized in that wherein the length of the inner needle is more than a path of the bore, and its exposed part outside of an opening of the bore is 0.5˜3.0 mm.
 6. The multi-axial expandable pedicle screw of claim 1, characterized in that wherein the length of the inner needle is more than the path of the bore, and its exposed part outside of an opening of the bore is 0.8˜1.5 mm.
 7. The multi-axial expandable pedicle screw of claim 1, characterized in that wherein the expansion gaps are of 60%-70% of the total length of the screw, structured by splitting grooves to form anterior fins, staring from the tip of the screw along its axial direction upward to the bore.
 8. The multi-axial expandable pedicle screw of claim 1, characterized in that wherein the expansion gaps have two or more fins; anterior fins are curve shaped.
 9. The multi-axial expandable pedicle screw of claim 1, characterized in that wherein the adapting piece in connection with the screw forms U shape in its entirety.
 10. The multi-axial expandable pedicle screw of claim 1, characterized in that wherein a regular polyhedron shaped concave is set up on the spherical shaped end of the screw.
 11. The multi-axial expandable pedicle screw of claim 1, characterized in that further comprising an additional annular pad being either an opening structure or an enclosed structure positioning in between the inner needle and the fixation rod.
 12. An expansion method of multi-axial expandable pedicle screw, comprising: adopting multi-axial, multi-angle connecting method with other medical parts; fulfilling press operation to the inner needle positioning in the bore of the screw through rod-press technique to controllably complete expansion process to the screw, enabling the screw to expand to 2˜3 mm based on the original diameter.
 13. The expansion method of multi-axial expandable pedicle screw according to claim 12, characterized in that wherein length of the inner needle positioning in the bore of the screw is more than the path of the bore, and its exposed part outside of an opening of the bore is 0.5˜3.0 mm.
 14. The expansion method of multi-axial expandable pedicle screw according to claim 13, characterized in that wherein length of the inner needle positioning in the bore of the screw is more than the path of the bore, and its exposed part outside of an opening of the bore is 0.8˜1.5 mm.
 15. The expansion method of multi-axial expandable pedicle screw according to claim 12, characterized in that further comprising expansion gaps being of 60%-70% of the total length of the screw, structured by splitting grooves to form anterior fins, staring from the tip of the screw along its axial direction upward to the bore.
 16. The expansion method of multi-axial expandable pedicle screw according to claim 15, characterized in that wherein adopting curve shaped anterior fins.
 17. The expansion method of multi-axial expandable pedicle screw according to claim 12, characterized in that inserting the inner needle in the bore.
 18. The expansion method of multi-axial expandable pedicle screw according to claim 12, characterized in that the inner needle and the bore to fit with are taper shaped at their tips respectively, in which an angle of the taper of the inner needle is equivalent to an angle of the taper of the bore at its tip or less; and the outer diameter of the inner needle matches the inside diameter of the bore. 